﻿// NOTE: See http://elegantcode.com/2011/03/02/wpf-advanced-jump-lists-using-a-single-instance-application/ for details.

//-----------------------------------------------------------------------
// <copyright file="SingleInstance.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <summary>
//     This class checks to make sure that only one instance of 
//     this application is running at a time.
// </summary>
//-----------------------------------------------------------------------

// ReSharper disable InconsistentNaming
// ReSharper disable StaticFieldInGenericType

namespace SolidMvvm {
	using System;
	using System.Collections;
	using System.Collections.Generic;
	using System.ComponentModel;
	using System.IO;
	using System.Runtime.InteropServices;
	using System.Runtime.Remoting;
	using System.Runtime.Remoting.Channels;
	using System.Runtime.Remoting.Channels.Ipc;
	using System.Runtime.Serialization.Formatters;
	using System.Security;
	using System.Text;
	using System.Threading;
	using System.Windows;
	using System.Windows.Threading;

	enum WM {
		NULL = 0x0000,

		CREATE = 0x0001,

		DESTROY = 0x0002,

		MOVE = 0x0003,

		SIZE = 0x0005,

		ACTIVATE = 0x0006,

		SETFOCUS = 0x0007,

		KILLFOCUS = 0x0008,

		ENABLE = 0x000A,

		SETREDRAW = 0x000B,

		SETTEXT = 0x000C,

		GETTEXT = 0x000D,

		GETTEXTLENGTH = 0x000E,

		PAINT = 0x000F,

		CLOSE = 0x0010,

		QUERYENDSESSION = 0x0011,

		QUIT = 0x0012,

		QUERYOPEN = 0x0013,

		ERASEBKGND = 0x0014,

		SYSCOLORCHANGE = 0x0015,

		SHOWWINDOW = 0x0018,

		ACTIVATEAPP = 0x001C,

		SETCURSOR = 0x0020,

		MOUSEACTIVATE = 0x0021,

		CHILDACTIVATE = 0x0022,

		QUEUESYNC = 0x0023,

		GETMINMAXINFO = 0x0024,

		WINDOWPOSCHANGING = 0x0046,

		WINDOWPOSCHANGED = 0x0047,

		CONTEXTMENU = 0x007B,

		STYLECHANGING = 0x007C,

		STYLECHANGED = 0x007D,

		DISPLAYCHANGE = 0x007E,

		GETICON = 0x007F,

		SETICON = 0x0080,

		NCCREATE = 0x0081,

		NCDESTROY = 0x0082,

		NCCALCSIZE = 0x0083,

		NCHITTEST = 0x0084,

		NCPAINT = 0x0085,

		NCACTIVATE = 0x0086,

		GETDLGCODE = 0x0087,

		SYNCPAINT = 0x0088,

		NCMOUSEMOVE = 0x00A0,

		NCLBUTTONDOWN = 0x00A1,

		NCLBUTTONUP = 0x00A2,

		NCLBUTTONDBLCLK = 0x00A3,

		NCRBUTTONDOWN = 0x00A4,

		NCRBUTTONUP = 0x00A5,

		NCRBUTTONDBLCLK = 0x00A6,

		NCMBUTTONDOWN = 0x00A7,

		NCMBUTTONUP = 0x00A8,

		NCMBUTTONDBLCLK = 0x00A9,

		SYSKEYDOWN = 0x0104,

		SYSKEYUP = 0x0105,

		SYSCHAR = 0x0106,

		SYSDEADCHAR = 0x0107,

		COMMAND = 0x0111,

		SYSCOMMAND = 0x0112,

		MOUSEMOVE = 0x0200,

		LBUTTONDOWN = 0x0201,

		LBUTTONUP = 0x0202,

		LBUTTONDBLCLK = 0x0203,

		RBUTTONDOWN = 0x0204,

		RBUTTONUP = 0x0205,

		RBUTTONDBLCLK = 0x0206,

		MBUTTONDOWN = 0x0207,

		MBUTTONUP = 0x0208,

		MBUTTONDBLCLK = 0x0209,

		MOUSEWHEEL = 0x020A,

		XBUTTONDOWN = 0x020B,

		XBUTTONUP = 0x020C,

		XBUTTONDBLCLK = 0x020D,

		MOUSEHWHEEL = 0x020E,

		CAPTURECHANGED = 0x0215,

		ENTERSIZEMOVE = 0x0231,

		EXITSIZEMOVE = 0x0232,

		IME_SETCONTEXT = 0x0281,

		IME_NOTIFY = 0x0282,

		IME_CONTROL = 0x0283,

		IME_COMPOSITIONFULL = 0x0284,

		IME_SELECT = 0x0285,

		IME_CHAR = 0x0286,

		IME_REQUEST = 0x0288,

		IME_KEYDOWN = 0x0290,

		IME_KEYUP = 0x0291,

		NCMOUSELEAVE = 0x02A2,

		DWMCOMPOSITIONCHANGED = 0x031E,

		DWMNCRENDERINGCHANGED = 0x031F,

		DWMCOLORIZATIONCOLORCHANGED = 0x0320,

		DWMWINDOWMAXIMIZEDCHANGE = 0x0321,

		#region Windows 7

		DWMSENDICONICTHUMBNAIL = 0x0323,

		DWMSENDICONICLIVEPREVIEWBITMAP = 0x0326,

		#endregion

		USER = 0x0400,

		// This is the hard-coded message value used by WinForms for Shell_NotifyIcon.
		// It's relatively safe to reuse.
		TRAYMOUSEMESSAGE = 0x800, //WM_USER + 1024

		APP = 0x8000
	}

	[SuppressUnmanagedCodeSecurity]
	static class NativeMethods {
		/// <summary>
		///     Delegate declaration that matches WndProc signatures.
		/// </summary>
		public delegate IntPtr MessageHandler(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled);

		public static string[] CommandLineToArgvW(string cmdLine) {
			IntPtr argv = IntPtr.Zero;
			try {
				int numArgs;

				argv = _CommandLineToArgvW(cmdLine, out numArgs);
				if (argv == IntPtr.Zero)
					throw new Win32Exception();
				var result = new string[numArgs];

				for (int i = 0; i < numArgs; i++) {
					IntPtr currArg = Marshal.ReadIntPtr(argv, i * Marshal.SizeOf(typeof(IntPtr)));
					result[i] = Marshal.PtrToStringUni(currArg);
				}

				return result;
			}
			finally {
				_LocalFree(argv);
				// Otherwise LocalFree failed.
				// Assert.AreEqual(IntPtr.Zero, p);
			}
		}

		[DllImport("shell32.dll", EntryPoint = "CommandLineToArgvW", CharSet = CharSet.Unicode)]
		static extern IntPtr _CommandLineToArgvW([MarshalAs(UnmanagedType.LPWStr)] string cmdLine, out int numArgs);

		[DllImport("kernel32.dll", EntryPoint = "LocalFree", SetLastError = true)]
		static extern IntPtr _LocalFree(IntPtr hMem);
	}

	public interface ISingleInstanceApp {
		bool SignalExternalCommandLineArgs(IList<string> args);
	}

	/// <summary>
	///     This class checks to make sure that only one instance of
	///     this application is running at a time.
	/// </summary>
	/// <remarks>
	///     Note: this class should be used with some caution, because it does no
	///     security checking. For example, if one instance of an app that uses this class
	///     is running as Administrator, any other instance, even if it is not
	///     running as Administrator, can activate it with command line arguments.
	///     For most apps, this will not be much of an issue.
	/// </remarks>
	public static class SingleInstance<TApplication> where TApplication : Application, ISingleInstanceApp {
		/// <summary>
		///     Suffix to the channel name.
		/// </summary>
		const string ChannelNameSuffix = "SingeInstanceIPCChannel";

		/// <summary>
		///     String delimiter used in channel names.
		/// </summary>
		const string Delimiter = ":";

		/// <summary>
		///     IPC protocol used (string).
		/// </summary>
		const string IpcProtocol = "ipc://";

		/// <summary>
		///     Remote service name.
		/// </summary>
		const string RemoteServiceName = "SingleInstanceApplicationService";

		/// <summary>
		///     IPC channel for communications.
		/// </summary>
		static IpcServerChannel channel;

		/// <summary>
		///     List of command line arguments for the application.
		/// </summary>
		static IList<string> commandLineArgs;

		/// <summary>
		///     Application mutex.
		/// </summary>
		static Mutex singleInstanceMutex;

		/// <summary>
		///     Gets list of command line arguments for the application.
		/// </summary>
		public static IList<string> CommandLineArgs
		{
			get
			{
				return commandLineArgs;
			}
		}

		/// <summary>
		///     Checks if the instance of the application attempting to start is the first instance.
		///     If not, activates the first instance.
		/// </summary>
		/// <returns>True if this is the first instance of the application.</returns>
		public static bool InitializeAsFirstInstance(string uniqueName) {
			commandLineArgs = GetCommandLineArgs(uniqueName);

			// Build unique application Id and the IPC channel name.
			string applicationIdentifier = uniqueName + Environment.UserName;

			string channelName = String.Concat(applicationIdentifier, Delimiter, ChannelNameSuffix);

			// Create mutex based on unique application Id to check if this is the first instance of the application. 
			bool firstInstance;
			singleInstanceMutex = new Mutex(true, applicationIdentifier, out firstInstance);
			if (firstInstance)
				CreateRemoteService(channelName);
			else
				SignalFirstInstance(channelName, commandLineArgs);

			return firstInstance;
		}

		/// <summary>
		///     Cleans up single-instance code, clearing shared resources, mutexes, etc.
		/// </summary>
		public static void Cleanup() {
			if (singleInstanceMutex != null) {
				singleInstanceMutex.Close();
				singleInstanceMutex = null;
			}

			if (channel != null) {
				ChannelServices.UnregisterChannel(channel);
				channel = null;
			}
		}

		/// <summary>
		///     Activates the first instance of the application with arguments from a second instance.
		/// </summary>
		/// <param name="args">List of arguments to supply the first instance of the application.</param>
		static void ActivateFirstInstance(IList<string> args) {
			// Set main window state and process command line args
			if (Application.Current == null)
				return;

			((TApplication)Application.Current).SignalExternalCommandLineArgs(args);
		}

		/// <summary>
		///     Callback for activating first instance of the application.
		/// </summary>
		/// <param name="arg">Callback argument.</param>
		/// <returns>Always null.</returns>
		static object ActivateFirstInstanceCallback(object arg) {
			// Get command line args to be passed to first instance
			var args = arg as IList<string>;
			ActivateFirstInstance(args);
			return null;
		}

		/// <summary>
		///     Creates a remote service for communication.
		/// </summary>
		/// <param name="channelName">Application's IPC channel name.</param>
		static void CreateRemoteService(string channelName) {
			var serverProvider = new BinaryServerFormatterSinkProvider();
			serverProvider.TypeFilterLevel = TypeFilterLevel.Full;
			IDictionary props = new Dictionary<string, string>();

			props["name"] = channelName;
			props["portName"] = channelName;
			props["exclusiveAddressUse"] = "false";

			// Create the IPC Server channel with the channel properties
			channel = new IpcServerChannel(props, serverProvider);

			// Register the channel with the channel services
			ChannelServices.RegisterChannel(channel, true);

			// Expose the remote service with the REMOTE_SERVICE_NAME
			var remoteService = new IPCRemoteService();
			RemotingServices.Marshal(remoteService, RemoteServiceName);
		}

		/// <summary>
		///     Gets command line args - for ClickOnce deployed applications, command line args may not be passed directly, they
		///     have to be retrieved.
		/// </summary>
		/// <returns>List of command line arg strings.</returns>
		static IList<string> GetCommandLineArgs(string uniqueApplicationName) {
			string[] args = null;
			if (AppDomain.CurrentDomain.ActivationContext == null) // The application was not clickonce deployed, get args from standard API's
				args = Environment.GetCommandLineArgs();
			else {
				// The application was clickonce deployed
				// Clickonce deployed apps cannot recieve traditional commandline arguments
				// As a workaround commandline arguments can be written to a shared location before 
				// the app is launched and the app can obtain its commandline arguments from the 
				// shared location               
				string appFolderPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), uniqueApplicationName);

				string cmdLinePath = Path.Combine(appFolderPath, "cmdline.txt");
				if (File.Exists(cmdLinePath))
					try {
						using (TextReader reader = new StreamReader(cmdLinePath, Encoding.Unicode))
							args = NativeMethods.CommandLineToArgvW(reader.ReadToEnd());

						File.Delete(cmdLinePath);
					}
					catch (IOException) {}
			}

			if (args == null)
				args = new string[] { };

			return new List<string>(args);
		}

		/// <summary>
		///     Creates a client channel and obtains a reference to the remoting service exposed by the server -
		///     in this case, the remoting service exposed by the first instance. Calls a function of the remoting service
		///     class to pass on command line arguments from the second instance to the first and cause it to activate itself.
		/// </summary>
		/// <param name="channelName">Application's IPC channel name.</param>
		/// <param name="args">
		///     Command line arguments for the second instance, passed to the first instance to take appropriate action.
		/// </param>
		static void SignalFirstInstance(string channelName, IList<string> args) {
			var secondInstanceChannel = new IpcClientChannel();
			ChannelServices.RegisterChannel(secondInstanceChannel, true);

			string remotingServiceUrl = IpcProtocol + channelName + "/" + RemoteServiceName;

			// Obtain a reference to the remoting service exposed by the server i.e the first instance of the application
			var firstInstanceRemoteServiceReference = (IPCRemoteService)RemotingServices.Connect(typeof(IPCRemoteService), remotingServiceUrl);

			// Check that the remote service exists, in some cases the first instance may not yet have created one, in which case
			// the second instance should just exit
			if (firstInstanceRemoteServiceReference != null) // Invoke a method of the remote service exposed by the first instance passing on the command line
				// arguments and causing the first instance to activate itself
				firstInstanceRemoteServiceReference.InvokeFirstInstance(args);
		}

		/// <summary>
		///     Remoting service class which is exposed by the server i.e the first instance and called by the second instance
		///     to pass on the command line arguments to the first instance and cause it to activate itself.
		/// </summary>
		class IPCRemoteService : MarshalByRefObject {
			/// <summary>
			///     Remoting Object's ease expires after every 5 minutes by default. We need to override the InitializeLifetimeService
			///     class
			///     to ensure that lease never expires.
			/// </summary>
			/// <returns>Always null.</returns>
			public override object InitializeLifetimeService() {
				return null;
			}

			/// <summary>
			///     Activates the first instance of the application.
			/// </summary>
			/// <param name="args">List of arguments to pass to the first instance.</param>
			public void InvokeFirstInstance(IList<string> args) {
				if (Application.Current != null) // Do an asynchronous call to ActivateFirstInstance function
					Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new DispatcherOperationCallback(ActivateFirstInstanceCallback), args);
			}
		}
	}
}

// ReSharper restore StaticFieldInGenericType
// ReSharper restore InconsistentNaming
